introduced new Context class. I've bumped up the next release to v4.7.0 because this is a relatively big mind shift in how the framework works, and it's a big enough API change to warrant a minor update. This is the first step towards enabling context tracing for stellar unit testing

Gruntfile.js

@@ -4,6 +4,7 @@ module.exports = function(grunt) {
     'src/Global.js', 
     'src/Util.js', 
     'src/Canvas.js',
+    'src/Context.js',
     'src/Factory.js',
     'src/Node.js', 
     'src/Animation.js',